|“||Power-Up Hearts have fallen throughout the land! Collect them to raise attack, health, and speed!”|
|— Guest Star ???? Star Allies Go! tutorial • Kirby Star Allies|
While each variant of Power-Up Heart has the same basic heart shape, each variant has a different design:
- Speed Power-Up Hearts are blue in color, dark blue on the left side and a lighter blue on the right. In the center of the heart is a white outline of a double right arrow. Blue sparkles orbit the surface of Speed Power-Up Hearts.
- Health Power-Up Hearts are green in color, dark green on the left side and a lighter green on the right side. In the center of the heart is a white outline of a shield. Green sparkles orbit the surface of Health Power-Up Hearts.
- Attack Power-Up Hearts are red in color, dark red on the left side and a lighter red on the right side. In the center of the heart is a white outline of a star-shaped explosion. Red sparkles orbit the surface of Attack Power-Up Hearts.
- All Power-Up Hearts are larger than Speed, Health, and Attack Power-Up Hearts, and they have a smaller heart attached to each bottom corners. All three hearts cycle between red, green, and blue. In the center of the large heart is a white star; the two smaller hearts are undecorated. Sparkles that cycle between red, green, and blue orbit the surface of All Power-Up Hearts.
Power-Up Hearts appear exclusively in the Guest Star ???? Star Allies Go! sub-game, where they replace rare Picture Pieces as the main collectible. At the beginning of each world, all the player's stats start at Level 1, and the player must raise those stats up to a maximum of Level 5 by collecting Power-Up Hearts. Every Power-Up Heart raises a stat by one level, and since all friends share the same stats, one player collecting a Power-Up Heart benefits everyone. At the end of each world, the stats revert back to Level 1; the only exception to this rule is in Far-Flung - Starlight Heroes, where the stats also reset halfway through the world, after Twin Kracko has been defeated.
There are often barely enough Power-Up Hearts to max out each stat, and as such, they are often hidden carefully; however, in cases where the player collects a Power-Up Heart when the respective stat is already maxed out, the item will have no effect. To obtain a Power-Up Heart, the player must either use a specific Friend Ability, press a Big Switch, clear a challenge in a Friend Action segment, or defeat a Room Guarder. Power-Up Hearts are usually located alongside two Picture Pieces. All Power-Up Hearts are the rarest variant; there are never more than two of them in any given world, and they very often require careful searching to obtain.
When the player obtains a Power-Up Heart, a fanfare plays, and the counter for the respective stat in the top-left corner of the HUD is increased. While Attack Power-Up Hearts have no immediate effect when collected, Health Power-Up Hearts and All Power-Up Hearts serve to completely refill the player's health; additionally, Speed Power-Up Hearts give the player a cosmetic afterimage whose length is proportional to their speed stat.
Before Level 1, a player's health bar is about half the regular size, and at Level 5, it becomes regular length; similarly, the initial speed stat is about half as much as the normal value, and increases to about twice as much at Level 5, and the same concept applies to the attack stat.